1. Field of the Invention
The present invention relates to light source control technology suitable for an electronic device that is worn on or carried by a user.
2. Description of the Related Art
In recent years, various products to be worn on the human body have been developed for recording and analyzing various data at the time of exercise such as running, cycling, swimming, or trekking or in daily lives, and so-called sports watches that are worn on the body of the user and has a function for providing a user with exercise data or the like collected and analyzed at the time of exercise have been available on the market. Furthermore, portable electronic devices such as portable telephones, smartphones (multifunctional portable telephones), and tablet terminals have been widely available. Most of these electronic devices include a display device for providing various information to its user.
Here, various types of display devices are applied in these portable electronic devices. As display devices for achieving high display quality and screen luminance, display devices including a transmission-type display panel and a backlight are often used. However, in these display devices, the power consumption of the backlight and an arithmetic circuit is generally large, whereby the driving time of the electronic device is disadvantageously shortened. In order to solve this problem, various methods have been proposed to save the power of the display devices including a backlight.
For example, Japanese Patent Application Laid-Open (Kokai) Publication No. 2014-142480 discloses a method in which a normal mode and a power saving mode are provided as operation modes of a display device. In the power saving mode, the amount of light emission of a backlight is controlled based on the characteristics of the luminance of light emitted from the backlight with respect to the luminance of video displayed on a display panel, whereby the power consumption is reduced while inhibiting a decrease in the luminance of the video.